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<head>
  <meta charset="UTF-8">
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  <title>Document</title>
  <style>
    html {
      font-size: 16px;;
    }
    .ems li{
      font-size: 1.3em;
    }
    .rems li {
      font-size: 1.3rem;
    }
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</head>
<body>
  <ul class="ems">
    <li>one</li>
    <li>two</li>
    <li>three
      <ul>
        <li>three 1</li>
        <li>three 2
          <ul>
            <li>three 2-1</li>
          </ul>
        </li>
      </ul>
    </li>
  </ul>
  <ul class="rems">
    <li>one</li>
    <li>two</li>
    <li>three
      <ul>
        <li>three 1</li>
        <li>three 2
          <ul>
            <li>three 2-1</li>
          </ul>
        </li>
      </ul>
    </li>
  </ul>
</body>
</html>